The current state of the art in refractive laser surgery involves ablating corneal tissue of the eye with an ultra-fast, ultra-short pulse duration laser beam. Indeed, it is well known that the ablation of selected corneal tissue can correct refractive errors of a patient's eye by permanently altering the structure of the cornea. A system for accomplishing this type of tissue ablation through laser surgery is disclosed in U.S. Pat. No. 6,610,051, entitled “A Device and Method for Performing Refractive Surgery,” which issued to Bille and is assigned to the same assignee as the present application, i.e. 20/10 Perfect Vision Optische Geraete GmbH.
Importantly, the nature of refractive laser surgery requires that the laser beam be precisely focused to a very small focal spot within the cornea. As such, the patient's eye must be stabilized, and the laser system must be properly and precisely aligned with the patient's eye. In order to achieve proper alignment between the eye of the patient and the laser system, the system alignment settings and operating parameters must be well defined, steadfastly maintained, and frequently verified. Further, as indicated above, it is well known to those skilled in the art that accurate and precise refractive surgery requires the corneal tissue be photoablated when the eye is substantially stabilized or stationary. As always, patient comfort and safety must be considered when holding the eye stationary and conducting the laser surgery.
In order to achieve the goal of maximizing results while minimizing risks to the patient during surgery, it is important to eliminate, or at least significantly reduce, as many system errors as possible. Included here is the improper alignment of the patient's eye, relative to the laser system. Interestingly, alignment errors may result from either a misconfiguration of the system, or from the patient's interaction with the system. Insofar as patient/system interaction is concerned, any voluntary or involuntary movement of the patient's eye during surgery can significantly alter the alignment of the eye relative to the laser system. It is necessary, therefore, to hold the eye of the patient stationary during any lasing procedure. Holding the eye stationary does not, however, necessarily require direct contact between the eye and the laser system. In fact, for several current laser surgery systems, the eye of the patient is not placed in physical contact with the laser system. When the eye is allowed to move independently of the system, however, maintaining an optical alignment of the eye with the laser system can be problematic. On the other hand, those systems wherein the eye of the patient is placed and held in direct contact with the laser system, maintaining optical alignment between the eye and the laser system, still poses problems.
For systems wherein a patient's eye is to be stabilized by placing the eye in direct contact with the system, stabilization can be established in either of two ways. For one, the patient can be pre-positioned as desired, and the system then moved into contact with the eye. Such systems, of course, must be capable of being reconfigured to establish the necessary optical alignment. For another, the laser system can be preconfigured with a desired optical alignment, and the patient then moved into contact with the system. Either way, there are alignment issues that need to be addressed. In the latter case, however, use of a preconfigured optical system avoids the difficulties that may arise due to extended displacements or altered orientations of the optical elements.
In addition to the operational issues discussed above, patient safety is always a concern. In particular, when the eye is in direct contact with the laser system, the magnitude of the interactive forces that are exerted on the eye are of concern. The several different events that can cause these forces to exceed the limits of safety need to be avoided.
In light of the above, it is an objective of the present invention to provide a system and method for positioning the eye of a patient relative to a laser system, for refractive laser surgery. Another object of the present invention is to provide a system and method for positioning the eye of a patient for refractive laser surgery, wherein alignment of the eye with the laser system is established by moving the patient, while the laser system remains stationary. Yet another object of the present invention is to provide a system and method for positioning the eye of a patient for refractive laser surgery which avoids damage to the eye while holding the eye substantially stationary during the laser surgery procedure. Still another object of the present invention is to provide a system and method for positioning the eye of a patient for refractive laser surgery that is easy to use, relatively simple to manufacture, and comparatively cost effective.